Heptanuclear cobalt(II) dicubane compounds with single-molecule magnet behavior

The reaction between the tetranuclear compound [Co4(tta)4(OMe)4(MeOH)4] (tta = 4,4,4-trifluoro-1-thienoyl-2,4-butanedionate) and isopropanol or n-butanol leads to two heptanuclear compounds with general molecular formula [Co7(OH)8(tta)6(ROH)6]·ROH (R = isopropyl, for 1 or n-butyl, for 2). The crystal structures of both heptamers consist of two cubane-like units linked through one shared cobalt(II) ion vertex. The reaction leads to the replacement of precursor methoxide bridges by hydroxo in the heptanuclear compounds, which connect the internal metal ion to the six external ones. The magnetic properties revealed moderate ferromagnetic interactions among the cobalt(II) ions. Furthermore, ac magnetic susceptibility measurements confirm that these compounds are new examples of single-molecule magnets (SMM) containing cobalt(II) ions, with an energy barrier for magnetization reversal of 22 K and 21 K, respectively for 1 and 2.